1. Field of the Invention
This invention relates to tools and machines for cutting a chamfer on the edge of a workpiece. The workpiece is typically a flat metal plate usually having a thickness ranging from 3/16" to 2". The cutting machine comprises a portable hand tool movable along the plate's edge to form a chamfered edge.
2. Prior Developments
Chamfering machines are designed to form chamfered edges on plates, blocks and pipe ends. Typically, the chamfering operation is performed by clamping the workpiece in a fixed position, and moving the chamfering machine by hand along the edge of the workpiece to form a chamfered edge.
The chamfering operation is often performed to remove burrs on the workpiece, or to increase the edge surface area prior to welding the workpiece to another mating piece. The chamfer provides a "V" groove at the juncture between the two pieces for achieving deeper and stronger welds.
The term "chamfering" is here used interchangeably with the term "beveling". Both terms are understood to mean a process whereby an edge of a workpiece is cut along its cross section to form a cross sectional edge angled obliquely to opposite faces of the workpiece.
U.S. Pat. Nos. 4,655,653, to Hall, et al; 5,028,179, to M. Grasset; and 4,881,857, to Y. Tanaka, illustrate typical prior art machines for forming chamfered edges on workpieces. Heck Industries, Inc. of Hartland, Mich. sells a beveling machine under the trademark BEVEL-MILL that uses a milling type cutter.
One problem with prior art chamfering machines is that the cutter has a relatively small diameter and relatively shallow cutting flutes. Typically the cutter diameter is less than 1/2"; the cutting depth is only a few thousandth's of an inch.
When the workpiece is a thick metal plate having a thickness of about 1/2", it is necessary to make several passes of the cutting machine along an edge of the workpiece in order to form a chamfered edge on the workpiece. After each pass, the guide mechanism on the machine has to be adjusted to achieve a desired cutting depth during the next pass. If the guide mechanism is not adjustable, then it becomes difficult to maintain a constant cutting depth along the entire length of the workpiece edge, so that the quality of the finished edge suffers.
The small diameter cutters used in prior art chamfering machines are usually powered by relatively small A.C. electric motors developing no more than about one half horsepower. Such motors are capable of powering the small diameter cutters used in prior art practice. However, such motors would not adequately power large diameter milling cutters, e.g. cutters having diameters on the order of 21/2", and cutting depths on the order of 0.100 inches. Such large diameter cutters, when adequately powered, perform a chamfering operation with a relatively small number of passes along the edge of the workpiece.
The present invention relates to a chamfering machine having a milling cutter having a relatively large diameter and a relatively large cutting depth, whereby the machine performs a chamfering operation with a relatively few passes of the machine along the edge of the workpiece.
The machine is preferably powered by an electric motor having a rating of at least two horsepower, whereby the milling cutter achieves a large cutting depth without overloading the motor. The motor is preferably a variable speed motor used previously for powering sanders and grinders. Such motors are available from various sources, e.g. Sioux Mfg., Black and Decker, and General Electric.
The chamfering machine includes a mechanism for adjusting the depth of cut, and a second adjusting mechanism for adjusting the slant angle of the chamfered edge. Typically, the slant angle of the chamfered edge can be varied between an angle of about 45.degree. (relative to the plane of the workpiece major surface) to an angle of about 15.degree.. The two adjusting mechanisms are separate and independent, such that one adjustment does not adversely affect the machine setting achieved with the other adjustment mechanism.
The machine is designed for a two-handed operation. A first handle extends from the motorized drive unit. A second handle (or knob) is mounted on a hood assembly that overlies the rotary milling cutter. The person operating the chamfering machine grasps the two handles (using two hands) and moves the machine along an edge surface of the workpiece to form a chamfered edge.
The chamfering machine is designed for an easy two-handed operation to easily and quickly achieve each cutting pass of the machine. An elongated V-shaped guide structure is incorporated into the machine, whereby the rotary cutter has a predetermined constant cutting depth along the workpiece edge during any given pass of the machine. The finished edge surface is smooth and flat, without ridges, valleys or other surface irregularities. The V-shaped guide structure is adjustable around the apex of the V, such that the slant angle of the chamfered edge surface can be changed or varied to meet different needs or requirements.